MSN's Virtual Earth technology is a direct competitor to Google's Google Earth, a desktop client slated to replace Google's current Keyhole software.

To use MSN Virtual Earth, which currently shows U.S.-based satellite images only, users are first prompted to download one time the Microsoft Location Finder client application. It is this piece of software that turns WiFi-enabled PCs into "location-determining devices" without the addition of any separate hardware.

The Location Finder determines a user's location, which is identified on a map. Search results then become tailored around that location.

MSN is planning to release a refreshed version of Virtual Earth every four months, company officials said. The next beta release of MSN Virtual Earth, due this fall, is set to incorporate oblique, or bird's-eye, imagery licensed from Pictometry International that will add cities, landmarks and points of interest to the product. The fall version also will add support for the Apple Macintosh platform, MSN officials said.

MSN Virtual Earth project manager Mark Law said that people mistakenly consider MSN Virtual Earth to be a consumer-based site only. But it also is a platform for developers Law said. This fall, Microsoft is planning to make the Virtual Earth application-programming interface available to developers. For now, developers who want to get a jump start can "hack" the product to obtain the necessary interface information, Law said.

Steve Lombardi, program manager for MSN Virtual Earth, said in a recent video interview on Virtual Earth that was posted to Microsoft's Channel 9 Web site that Virtual Earth will eventually replace Microsoft's MapPoint service. At first, however, the two services will continue to run in parallel. MapPoint covers 30 countries with street-level data, while Virtual Earth at this point only covers the United States.

Microsoft Chairman Bill Gates introduced MSN Virtual Earth as a new satellite imagery component of their expanding search technologies, at the D: Conference in May, with promises to go live in early July. Microsoft merged its MSN Virtual Earth and MSN Search teams in June and released a private beta of MSN Local Search at that time.

Google began incorporating satellite images in April of this year after launching its first local search in late 2004.

Microsoft has not said when it intends to move MSN Virtual Earth from beta to final status.